Molecular sieve materials, both natural and synthetic, have catalytic properties for various types of hydrocarbon conversion. Certain molecular sieves (e.g., zeolites, AlPOs, and/or mesoporous materials) are ordered, porous crystalline materials having a definite crystalline structure. Within the crystalline molecular sieve material there are a large number of cavities which may be interconnected by a number of channels or pores. These cavities and pores are uniform in size within a specific molecular sieve material. Since the dimensions of these pores are such as to accept for adsorption molecules of certain dimensions while rejecting those of larger dimensions, these materials have come to be known as “molecular sieves” and are utilized in a variety of industrial processes.
Such molecular sieves, both natural and synthetic, include a wide variety of positive ion-containing crystalline oxides of tetravalent element. These oxides of tetravalent element can be described as a rigid three-dimensional framework of YO4 and a trivalent element oxide, such as a Group 13 element oxide (e.g., AlO4) (as defined in the Periodic Table, Chemical and Engineering News, 63(5), 27 (1985)). The tetrahedra are cross-linked by the sharing of oxygen atoms whereby the ratio of the total trivalent element (e.g., aluminum) and tetravalent atoms to oxygen atoms is 1:2. The electrovalence of the tetrahedra containing the trivalent element (e.g., aluminum) is balanced by the inclusion in the crystal of a cation, for example a proton, an alkali metal or an alkaline earth metal cation. This can be expressed as the ratio of the trivalent element (e.g., aluminum) to the number of various cations, such as H+, Ca2+/2, Sr2+/2, Na+, K+, or Li+, being equal to unity.
Molecular sieves that find application in catalysis include any of the naturally occurring or synthetic crystalline molecular sieves. Examples of these sieves include large pore zeolites, intermediate pore size zeolites, and small pore zeolites. These zeolites and their isotypes are described in “Atlas of Zeolite Framework Types”, eds. W. H. Meier, D. H. Olson and Ch. Baerlocher, Elsevier, Fifth Edition, 2001, which is herein incorporated by reference. A large pore zeolite generally has a pore size of at least about 7 Å and includes LTL, VFI, MAZ, FAU, OFF, *BEA, and MOR framework type zeolites (IUPAC Commission of Zeolite Nomenclature). Examples of large pore zeolites include mazzite, offretite, zeolite L, VPI-5, zeolite Y, zeolite X, omega, and zeolite beta. An intermediate pore size zeolite generally has a pore size from about 5 Å to less than about 7 Å and includes, for example, MFI, MEL, EUO, MTT, MFS, AEL, AFO, HEU, FER, MWW, and TON framework type zeolites (IUPAC Commission of Zeolite Nomenclature). Examples of intermediate pore size zeolites include ZSM-5, ZSM-11, ZSM-22, “MCM-22 family material”, silicalite 1, and silicalite 2. A small pore size zeolite has a pore size from about 3 Å to less than about 5.0 Å and includes, for example, CHA, ERI, KFI, LEV, SOD, and LTA framework type zeolites (IUPAC Commission of Zeolite Nomenclature). Examples of small pore zeolites include ZK-4, ZSM-2, SAPO-34, SAPO-35, ZK-14, SAPO-42, ZK-21, ZK-22, ZK-5, ZK-20, zeolite A, chabazite, zeolite T, gmelinite, ALPO-17, and clinoptilolite.
The term “MCM-22 family material” (or “material of the MCM-22 family” or “molecular sieve of the MCM-22 family”), as used herein, includes one or more of:    (i) molecular sieves made from a common first degree crystalline building block unit cell, which unit cell has the MWW framework topology. (A unit cell is a spatial arrangement of atoms which if tiled in three-dimensional space describes the crystal structure. Such crystal structures are discussed in the “Atlas of Zeolite Framework Types”, Fifth edition, 2001, the entire content of which is incorporated as reference);    (ii) molecular sieves made from a common second degree building block, being a 2-dimensional tiling of such MWW framework topology unit cells, forming a monolayer of one unit cell thickness, preferably one c-unit cell thickness;    (iii) molecular sieves made from common second degree building blocks, being layers of one or more than one unit cell thickness, wherein the layer of more than one unit cell thickness is made from stacking, packing, or binding at least two monolayers of one unit cell thickness. The stacking of such second degree building blocks can be in a regular fashion, an irregular fashion, a random fashion, or any combination thereof; and    (iv) molecular sieves made by any regular or random 2-dimensional or 3-dimensional combination of unit cells having the MWW framework topology.
The MCM-22family materials are characterized by having an X-ray diffraction pattern including d-spacing maxima at 12.4±0.25, 3.57±0.07 and 3.42±0.07 Angstroms (either calcined or as-synthesized). The MCM-22 family materials may also be characterized by having an X-ray diffraction pattern including d-spacing maxima at 12.4±0.25, 6.9±0.15, 3.57±0.07 and 3.42±0.07 Angstroms (either calcined or as-synthesized). The X-ray diffraction data used to characterize the molecular sieve are obtained by standard techniques using the K-alpha doublet of copper as the incident radiation and a diffractometer equipped with a scintillation counter and associated computer as the collection system. Materials belong to the MCM-22 family include MCM-22 (described in U.S. Pat. No. 4,954,325 and U.S. patent application Ser. No. 11/823,722 now U.S. Pat. No. 7,883,686), PSH-3 (described in U.S. Pat. No. 4,439,409), SSZ-25 (described in U.S. Pat. No. 4,826,667), ERB-1 (described in European Patent No. 0293032), ITQ-1 (described in U.S. Pat. No. 6,077,498), ITQ-2 (described in International Patent Publication No. W097117290), ITQ-30 (described in International Patent Publication No. W02005118476), MCM-36 (described in U.S. Pat. No. 5,250,277), MCM-49 (described in U.S. Pat. No. 5,236,575), UZM-8 described in U.S. Pat. No. 6,756,030), MCM-56 (described in U.S. Pat. No. 5,362,697), EMM-10-P (described in U.S. patent application Ser. No. 11/823,129 now U.S. Pat. No. 7,959,899), and EMM-10 (described in U.S. patent application Ser. No. 11/824,742 now U.S. Pat. No. 8,110,176 and Ser. No. 11/827,953 now U.S. Pat. No. 7,842,277). The entire contents of the patents are incorporated herein by reference.
It is to be appreciated the MCM-22 family molecular sieves described above are distinguished from conventional large pore zeolite alkylation catalysts, such as mordenite, in that the MCM-22 materials have 12-ring surface pockets which do not communicate with the 10-ring internal pore system of the molecular sieve.
The zeolitic materials designated by the IZA-SC as being of the MWW topology are multi-layered materials which have two pore systems arising from the presence of both 10 and 12 membered rings. The Atlas of Zeolite Framework Types classes five differently named materials as having this same topology: MCM-22, ERB-1, ITQ-1, PSH-3, and SSZ-25.
The MCM-22 family molecular sieves have been found to be useful in a variety of hydrocarbon conversion processes. Examples of MCM-22 family molecular sieve are MCM-22, MCM-49, MCM-56, ITQ-1, PSH-3, SSZ-25, and ERB-1. Such molecular sieves are useful for alkylation of aromatic compounds. For example, U.S. Pat. No. 6,936,744 discloses a process for producing a monoalkylated aromatic compound, particularly cumene, comprising the step of contacting a polyalkylated aromatic compound with an alkylatable aromatic compound under at least partial liquid phase conditions and in the presence of a transalkylation catalyst to produce the monoalkylated aromatic compound, wherein the transalkylation catalyst comprises a mixture of at least two different crystalline molecular sieves, wherein each of said molecular sieves is selected from zeolite beta, zeolite Y, mordenite and a material having an X-ray diffraction pattern including d-spacing maxima at 12.4±0.25, 6.9±0.15, 3.57±0.07 and 3.42±0.07 Angstrom (Å).
The MCM-22 family molecular sieves including MCM-22, MCM-49, and MCM-56 have various applications in hydrocarbon conversion processes. Unfortunately, industrial applications of zeolite catalysts have been hindered due to some major disadvantages associated with the current synthesis techniques that make large scale production of these catalysts complicated and therefore expensive. At present, crystalline zeolite catalysts are synthesized mainly by conventional liquid-phase hydrothermal treatment, including in-situ crystallization and seeding method, and the vapor phase transport method.
In the hydrothermal method, a reaction mixture of silica, alumina, caustic agent, an organic template or structure directing agent, and water is heated at a high temperature in a liquid phase to produce crystalline zeolite crystals (e.g., described in U.S. Pat. No. 5,871,650). The product is recovered by filtration and washing followed by calcination.
U.S. Pat. No. 5,558,851 discloses a method for preparing a crystalline aluminosilicate zeolite from a reaction mixture containing only sufficient water so that the reaction mixture may be shaped if desired. In the method, the reaction mixture is heated at crystallization conditions and in the absence of an external liquid phase, so that excess liquid need not be removed from the crystallized material prior to drying the crystals.
U.S. Pat. No. 6,099,820 discloses a method for preparing a crystalline zeolite having the X-ray diffraction lines of Table 1 of the U.S. Pat. No. 6,099,820. The method includes preparing a template-free reaction mixture including at least one active source of a first oxide selected from the group consisting of an oxide of silicon, germanium or both, optionally at least one active source of a second oxide selected from the group consisting of an oxide of aluminum, boron, gallium, iron or a mixture thereof; and heating the reaction mixture at crystallization conditions for sufficient time to form a crystallized material containing zeolite crystals having the X-ray diffraction lines of Table 1 of the U.S. Pat. No. 6,099,820, where said zeolite crystals have a first oxide/second oxide molar ratio greater than 12.
U.S. Pat. Nos. 5,665,325, 6,864,203, 6,039,864, 6,958.305, and 6,977,320 disclose a binder-free zeolite (or zeolite-bound-zeolite) process for producing substantially binder-free zeolites, and the use of these zeolites in catalysis and in separation processes.
U.S. Pat. No. 5,871,650 discloses a new zeolite membrane which exhibits a columnar cross-sectional morphology and preferred crystallographic orientation comprising a porous substrate having coated thereon a mesoporous growth enhancing layer and a layer of columnar zeolite crystals on said mesoporous growth enhancing layer, and wherein said mesoporous growth enhancing layer comprises nanocrystalline or colloidal sized zeolites, nanocrystalline or colloidal zeolite and metal oxide, or nanocrystalline or colloidal zeolite and colloidal metal, or nanocrystalline or colloidal zeolite, colloidal metal and metal oxide, and wherein said mesoporous growth enhancing layer has interstices of about 20 to about 2000 Å, and wherein said columnar zeolite layer is a polycrystalline layer wherein 99.9% of said columnar zeolite crystals have at least one point between adjacent crystals that is <20 Å. This disclosure is further directed to a process of producing a zeolite membrane exhibiting a columnar crystallographic orientation.
U.S. Pat. No. 5,895,769 discloses a new zeolite containing composition and a process for preparing the same. The composition is unique in that the zeolite crystals making up one layer of the composition pack in a manner such that the composition is essentially continuous with no large scale voids even when the zeolite layer is <10 μm thick. This disclosure is directed toward a composition comprised of a porous substrate and a layer of zeolite crystals wherein said layer of zeolite crystals is a polycrystalline layer with at least 99% of said zeolite crystals having at least one point between adjacent crystals that is ≦20 Å and wherein at least 90% of said crystals have widths of from about 0.2 to about 100 microns (preferably about 2 to about 50 microns) and wherein at least 75% of said crystals have a thickness of within 20% of the average crystal thickness. Preferably the composition has at most 1 volume % voids in the zeolite layer. Use of the composition is also described.
U.S. Pub. 2007-0191658 A1 discloses an improved vapor phase crystallization process by:    (a) providing a reaction mixture comprising at least one source of ions of tetravalent element Y, at least one source of alkali metal hydroxide, water, optionally at least one seed crystal, and optionally at least one source of ions of trivalent element X, said reaction mixture having the following mole composition:            Y:X2=10 to infinity        OH−:Y=0.001 to 2        M−:Y=0.001 to 2        wherein Y is a tetravalent element, X is a trivalent element, M is an alkali metal and the amount of water is at least sufficient to permit extrusion of said reaction mixture;            (b) extruding said reaction mixture to form a pre-formed extrudate; and    (c) crystallizing said pre-formed extrudate under vapor phase conditions in a reactor to form said crystalline molecular sieve whereby excess alkali metal hydroxide is removed from the pre-formed extrudate during crystallization.
There is a need for high throughput molecular sieve compositions made by crystallization of pre-formed extrudates in a liquid medium comprising water under liquid phase crystallization conditions, said molecular sieve compositions having at least one crystalline molecular sieve and optionally a non-molecular sieve portion. Methods are needed to enable large quantities of molecular sieve compositions to be produced with higher utilization of organic template and silica, while advantageously generating less wastewater as compared to known vapor phase methods. Also, improved methods are needed which minimize post-synthesis purification steps and simplify reactor design. This disclosure meets these and other needs.